Reversal of neuromuscular blockade by sugammadex does not affect EEG derived indices of depth of anesthesia

The Influence of Electromyographic on Electroencephalogram-Based Monitoring: Putting the Forearm on the Forehead

BACKGROUND

Monitoring the electroencephalogram (EEG) during general anesthesia can help to safely navigate the patient through the procedure by avoiding too deep or light anesthetic levels. In daily clinical practice, the EEG is recorded from the forehead and available neuromonitoring systems translate the EEG information into an index inversely correlating with the anesthetic level. Electrode placement on the forehead can lead to an influence of electromyographic (EMG) activity on the recorded signal in patients without neuromuscular blockade (NMB). A separation of EEG and EMG in the clinical setting is difficult because both signals share an overlapping frequency range. Previous research showed that indices decreased when EMG was absent in awake volunteers with NMB. Here, we investigated to what extent the indices changed, when EEG recorded during surgery with NMB agents was superimposed with EMG.

METHODS

We recorded EMG from the flexor muscles of the forearm of 18 healthy volunteers with a CONOX monitor during different activity settings, that is, during contraction using a grip strengthener and during active diversion (relaxed arm). Both the forehead and forearm muscles are striated muscles. The recorded EMG was normalized by z -scoring and added to the EEG in different amplification steps. The EEG was recorded during anesthesia with NMB. We replayed these combined EEG and EMG signals to different neuromonitoring systems, that is, bispectral index (BIS), CONOX with qCON and qNOX, and entropy module with state entropy (SE) and response entropy (RE). We used the Friedman test and a Tukey-Kramer post hoc correction for statistical analysis.

RESULTS

The indices of all neuromonitoring systems significantly increased when the EEG was superimposed with the contraction EMG and with high EMG amplitudes, the monitors returned invalid values, representative of artifact contamination. When replaying the EEG being superimposed with "relaxed" EMG, the qCON and BIS showed significant increases, but not SE and RE. For SE and RE, we observed an increased number of invalid values.

CONCLUSIONS

With our approach, we could show that EMG activity during contraction and resting state can influence the neuromonitoring systems. This knowledge may help to improve EEG-based patient monitoring in the future and help the anesthesiologist to use the neuromonitoring systems with more knowledge regarding their function.

The arousal effect of sugammadex reversal of neuromuscular blockade differs with anesthetic depth in propofol-remifentanil anesthesia: a randomized controlled trial

Sugammadex reverses neuromuscular blockade by encapsulating steroidal neuromuscular blockers; therefore, it does not pharmacologically affect sedation levels. However, some clinicians avoid using it because of sudden unwanted acting out or patient arousal. Previous studies suggested sugammadex-induced awakening, but frontal muscle contraction after sugammadex administration compromised reliability of results obtained from EEG-based anesthesia depth monitoring tools like bispectral index (BIS). We hypothesized that sugammadex would affect patients' arousal depending on their baseline levels of sedation. We evaluated arousal signs after sugammadex administration with BIS between 25 - 35 and 45 - 55 under steady-state propofol-remifentanil anesthesia at the end of a surgery (n = 33 in each group). After sugammadex administration, twelve patients with a BIS of 45 - 55 showed clinical signs of awakening but none with a BIS of 25 - 35 (36.4% vs. 0%, P = 0.001). The distribution of the modified observer's assessment of alertness/sedation scale scores was also significantly different between the two groups (P < 0.001). Changes in the BIS were significantly greater in the BIS 45 - 55 than in the 25 - 35 group (median difference, 7; 95% CI 2 - 19, P = 0.002). Arousal after sugammadex was affected by patient sedation levels, and clinical signs of awakening appeared only in those with BIS 45 - 55. Unwanted arousal of the patient should be considered when using sugammadex under shallow anesthesia.Clinical trial registry number: Clinical Trial Registry of Korea ( https://cris.nih.go.kr ; Principal investigator: Jieae Kim; Registration number: KCT0006248; Date of first registration: 11/06/2021).

Performance of the bispectral index and electroencephalograph derived parameters of anesthetic depth during emergence from xenon and sevoflurane anesthesia

Many processed EEG monitors (pEEG) are unreliable when non-GABAergic anesthetic agents are used. The primary aim of the study was to compare the response of the Bispectral Index (BIS) during emergence from anesthesia maintained by xenon and sevoflurane. To better understand the variation in response of pEEG to these agents, we also compared several EEG derived parameters relevant to pEEG monitoring during emergence. Twenty-four participants scheduled for lithotripsy were randomized to receive xenon or sevoflurane anesthesia. Participants were monitored with the BIS and had simultaneous raw EEG collected. BIS index values were compared at three key emergence timepoints: first response, eyes open and removal of airway. Two sets of EEG derived parameters, three related to the BIS: relative beta ratio, SynchFastSlow and SynchFastSlow biocoherence, and two unrelated to the BIS: spectral edge frequency and the composite cortical state, were calculated for comparison. BIS index values were significantly lower in the xenon group than the sevoflurane group at each emergence timepoint. The relative beta ratio parameter increased significantly during emergence in the sevoflurane group but not in the xenon group. The spectral edge frequency and composite cortical state parameters increased significantly in both groups during emergence. The BIS index is lower at equivalent stages of behavioural response during emergence from xenon anesthesia when compared to sevoflurane anesthesia, most likely due to differences in how these two agents influence the relative beta ratio. The spectral edge frequency and composite cortical state might better reflect emergence from xenon anaesthesia.Clinical trial number and registry Australia New Zealand Clinical Trials Registry Number: ACTRN12618000916246.

Comparison of Bispectral Index and Patient State Index values according to recovery from moderate neuromuscular block under steady-state total intravenous anesthesia

There were insufficient researches of the comparison between Bispectral Index (BIS) and Patient State Index (PSI) values during the recovery of moderate NMB. We investigated the response of these indices during neuromuscular blockade (NMB) reversal by sugammadex under steady-state total intravenous anesthesia (TIVA) using propofol/remifentanil. In this prospective, observational study, patients undergoing laparoscopic cholecystectomy were enrolled. At the end of surgery, after confirming that train-of-four (TOF) count as 1 or 2, we maintained a steady state (BIS value of 40-50). After administration of 2 mg kg^-1 sugammadex, BIS, PSI, and electromyography (EMG) signal values were recorded at one-minute intervals for 10 min. The primary outcome was the difference between the changes in BIS and PSI from baseline to a TOF ratio (TOFR) of 90 after sugammadex administration in steady-state TIVA. A total of 48 patients completed this trial. There was no significant difference between the changes in BIS and PSI values from baseline to TOFR 90 (- 0.333 ± 4.955 vs. - 0.188 ± 4.616; 95% confidence interval [CI] - 2.095 to 1.803; p = 0.882). Both BIS-EMG and PSI-EMG values at baseline and TOFR 90 were not statistically different (95% CI - 0.550 to 1.092; p = 0.510, 95% CI - 1.569 to 0.527; p = 0.322, respectively). No patient experienced any complications. Changes in BIS and PSI values after NMB reversal during steady-state TIVA were not significantly different. Both BIS and PSI provide trustworthy values for monitoring anesthetic depth during NMB reversal under TIVA.Trial Registration: This study was registered in the Clinical Trial Registry of Korea ( https://cris.nih.go.kr : KCT 0003805).

Intravenous infusion of rocuronium bromide prolongs emergence from propofol anesthesia in rats

BACKGROUND

Neuromuscular blocking agents induce muscle paralysis via the prevention of synaptic transmission at the neuromuscular junction and may have additional effects at other sites of action. With regard to potential effects of neuromuscular blocking agents on the central nervous system, a definitive view has not been established. We investigated whether intravenous infusion of rocuronium bromide affects the emergence from propofol anesthesia.

METHODS

Using an in vivo rat model, we performed propofol infusion for 60 minutes, along with rocuronium bromide at various infusion rates or normal saline. Sugammadex or normal saline was injected at the end of the infusion period, and we evaluated the time to emergence from propofol anesthesia. We also examined the neuromuscular blocking, circulatory, and respiratory properties of propofol infusion along with rocuronium bromide infusion to ascertain possible factors affecting emergence.

RESULTS

Intravenous infusion of rocuronium bromide dose-dependently increased the time to emergence from propofol anesthesia. Sugammadex administered after propofol infusion not containing rocuronium bromide did not affect the time to emergence. Mean arterial pressure, heart rate, partial pressures of oxygen and carbon dioxide, and pH were not affected by rocuronium bromide infusion. Neuromuscular blockade induced by rocuronium bromide, even at the greatest infusion rate in the emergence experiment, was rapidly antagonized by sugammadex.

CONCLUSIONS

These results suggest that intravenous infusion of rocuronium bromide dose-dependently delays the emergence from propofol anesthesia in rats. Future studies, such as detection of rocuronium in the cerebrospinal fluid or central nervous system, electrophysiologic studies, microinjection of sugammadex into the brain, etc., are necessary to determine the mechanism of this effect.

Multiparametric Monitoring of Hypnosis and Nociception-Antinociception Balance during General Anesthesia-A New Era in Patient Safety Standards and Healthcare Management

The development of general anesthesia techniques and anesthetic substances has opened new horizons for the expansion and improvement of surgical techniques. Nevertheless, more complex surgical procedures have brought a higher complexity and longer duration for general anesthesia, which has led to a series of adverse events such as hemodynamic instability, under- or overdosage of anesthetic drugs, and an increased number of post-anesthetic events. In order to adapt the anesthesia according to the particularities of each patient, the multimodal monitoring of these patients is highly recommended. Classically, general anesthesia monitoring consists of the analysis of vital functions and gas exchange. Multimodal monitoring refers to the concomitant monitoring of the degree of hypnosis and the nociceptive-antinociceptive balance. By titrating anesthetic drugs according to these parameters, clinical benefits can be obtained, such as hemodynamic stabilization, the reduction of awakening times, and the reduction of postoperative complications. Another important aspect is the impact on the status of inflammation and the redox balance. By minimizing inflammatory and oxidative impact, a faster recovery can be achieved that increases patient safety. The purpose of this literature review is to present the most modern multimodal monitoring techniques to discuss the particularities of each technique.

Impact of Sugammadex Versus Neostigmine/Glycopyrrolate on Perioperative Efficiency

Purpose

Neuromuscular blockade in the operating room necessitates the utilization of reversal agents to accelerate postoperative recovery and sustain operating room patient throughput. Cholinesterase inhibitors represent the historical standard of care for neuromuscular blockade reversal within anesthesia practice. Sugammadex, a synthetic gamma-cyclodextrin, was introduced to the market with evidence of more rapid and predictable reversal of neuromuscular blockade compared to alternative agents. Higher medication acquisition costs have limited more extensive use of sugammadex compared to that of neostigmine/glycopyrrolate. The purpose of this study was to examine the impact of sugammadex versus neostigmine/glycopyrrolate on perioperative efficiency to validate medication acquisition cost value.

Methods

A retrospective investigation was performed of patients with a surgical procedure at Houston Methodist Hospital from July 31, 2017 through August 1, 2018. The primary endpoint was time from reversal medication administration to operating room exit. Patient-specific doses were assessed to calculate average medication acquisition costs. The economic benefits of sugammadex were measured through review of average operating room and postanesthesia care unit costs per minute.

Results

There were a total of 640 surgical cases at Houston Methodist Hospital eligible for inclusion into the research study. The time from medication administration to operating room exit was significantly faster for sugammadex compared to neostigmine/glycopyrrolate (P<0.001) upon univariate analysis. However, when measured with linear regression, the difference in operating room exit time between sugammadex and neostigmine/glycopyrrolate was no longer statistically significant (P=0.122). Medication acquisition cost review highlighted a difference of $178.20, favoring use of neostigmine/glycopyrrolate.

Conclusion

The utilization of sugammadex does not correlate to consequential time saved in the operating room or extrapolation to workflow capacity for increased surgical case volume. Consideration of the medication acquisition cost promotes more restrictive use of sugammadex to indications with clinical relevance.

Effect of neuromuscular blockade on the bispectral index in critically ill patients

INTRODUCTION

It has been suggested that neuromuscular blockade (NMB) affects the capacity of bispectral index (BIS) monitoring to measure consciousness in sedated children. Our aim was to analyse the impact of NMB on BIS values in critically ill children.

METHODS

We conducted a prospective observational study of children monitored with a BIS system that received a continuous infusion of vecuronium. We analysed data on clinical, diagnostic and haemodynamic variables, sedatives, analgesics, muscle relaxants, and BIS parameters. We compared BIS parameters before the use of a muscle relaxant, during its administration, before its discontinuation and for the 24h following the end of the infusion.

RESULTS

The analysis included 35 patients (median age, 30 months). The most common diagnosis was heart disease (85%). The most frequent indication for initiation of NMB was low cardiac output (45%), followed by adaptation to mechanical ventilation (20%). Neuromuscular blockade did not produce a significant change in BIS values. We found a decrease was observed in electromyography (EMG) values at 6h (34.9±9.4 vs 31.2±7; P=.008) and 12h after initiation of NMB (34.9±9.4 vs 28.6±4.8; P =.006). We observed a small significant increase in BIS after discontinuation of NMB (from 42.7±11 to 48.4±14.5, P=.001), and 6 and 12h later (51.3±16.6; P=.015). There were no differences in the doses of sedatives or analgesics except for fentanyl, of which the dose was lowered after discontinuation of vecuronium.

CONCLUSION

Continuous NMB produces small changes on BIS values that are not clinically significant and therefore does not interfere with BIS consciousness monitoring in critically ill children.

Recovery from Anesthesia after Robotic-Assisted Radical Cystectomy: Two Different Reversals of Neuromuscular Blockade

During robot-assisted radical cystectomy (RARC), specific surgical conditions (a steep Trendelenburg position, prolonged pneumoperitoneum, effective myoresolution until the final stages of surgery) can seriously impair the outcomes. The aim of the study was to evaluate the incidence of postoperative nausea and vomiting (PONV) and ileus and the quality of cognitive function at the awakening in two groups of patients undergoing different reversals. In this randomized trial, patients that were American Society of Anesthesiologists physical status (ASA) ≤III candidates for RARC for bladder cancer were randomized into two groups: In the sugammadex (S) group, patients received 2 mg/kg of sugammadex as reversal of neuromuscolar blockade; in the neostigmine (N) group, antagonization was obtained with neostigmine 0.04 mg/kg + atropine 0.02 mg/kg. PONV was evaluated at 30 min, 6 and 24 h after anesthesia. Postoperative cognitive functions and time to resumption of intestinal transit were also investigated. A total of 109 patients were analyzed (54 in the S group and 55 in the N group). The incidence of early PONV was lower in the S group but not statistically significant (S group 25.9% vs. N group 29%; p = 0.711). The Mini-Mental State test mean value was higher in the S group vs. the N group (1 h after surgery: 29.3 (29; 30) vs. 27.6 (27; 30), p = 0.007; 4 h after surgery: 29.5 (30; 30) vs. 28.4 (28; 30), p = 0.05). We did not observe a significant decrease of the PONV after sugammadex administration versus neostigmine use. The Mini-Mental State test mean value was greater in the S group.

Effects of neuromuscular blockade reversal on bispectral index and frontal electromyogram during steady-state desflurane anesthesia: a randomized trial

The degree of neuromuscular blockade reversal may affect bispectral index (BIS) value. One possible reason is that the reverse of neuromuscular blockade affects electromyographic (EMG) signals of fascial muscle. Another reason is, the afferentation theory, the reverse of neuromuscular blockade relieves block signals generated in muscle stretch receptors from accessing the brain through afferent nerve pathways and induces arousal. Inaccurate BIS value may lead to overdose of drugs or the risk of intraoperative awareness. We compared changes in BIS and EMG values according to neuromuscular blockade reversal agents under steady-state desflurane anesthesia. A total of 65 patients were randomly allocated to receive either neostigmine 0.05 mg/kg, sugammadex 4 mg/kg, or pyridostigmine 0.25 mg/kg for neuromuscular blockade reversal under stable desflurane anesthesia, and 57 patients completed the study. The primary outcome was change in BIS and EMG values before and after administration of neuromuscular blockade reversal agents (between train-of-four [TOF] count 1-2 and TOF ratio 0.9). The change in BIS and EMG values before and after administration of neuromuscular blockade reversal agents were statistically different in each group (BIS: Neostigmine group, P < 0.001; Sugammadex group, P < 0.001; Pyridostigmine group, P = 0.001; EMG: Neostigmine group, P = 0.001; Sugammadex group, P < 0.001; Pyridostigmine group, P = 0.001; respectively). The BIS and EMG values had a positive correlation (P < 0.001). Our results demonstrate that the EMG and BIS values have increased after neuromuscular blockade reversal under desflurane anesthesia regardless of the type of neuromuscular blockade reversal agent. BIS should be applied carefully to measure of depth of anesthesia after neuromuscular blockade reversal.

Spectral entropy in monitoring anesthetic depth

Monitoring the brain response to hypnotics in general anesthesia, with the nociceptive and hemodynamic stimulus interaction, has been a subject of intense investigation for many years. Nowadays, monitors of depth of anesthesia are based in processed electroencephalogram by different algorithms, some of them unknown, to obtain a simplified numeric parameter approximate to brain activity state in each moment. In this review we evaluate if spectral entropy suitably reflects the brain electric behavior in response to hypnotics and the different intensity nociceptive stimulus effect during a surgical procedure.

Operating room discharge after deep neuromuscular block reversed with sugammadex compared with shallow block reversed with neostigmine: a randomized controlled trial

OBJECTIVE

To determine if reversing a deep or moderate block with sugammadex, compared with a shallow block reversed with neostigmine, reduces the time to operating room discharge after surgery and the time spent in the postanesthesia care unit.

DESIGN

A randomized controlled trial.

SETTING

Monocentric study performed from February 2011 until May 2012.

PATIENTS

One hundred consenting women with American Society of Anesthesiologists grade I or II were randomized into 2 groups.

INTERVENTION

Laparoscopic hysterectomy was performed under desflurane general anesthesia. For the neostigmine (N) group, 0.45 mg · kg^-1 rocuronium was followed by spontaneous recovery. A 5-mg rescue bolus was administered only if surgical evaluation was unacceptable. At the end of surgery, 50 μg · kg^-1 neostigmine with glycopyrrolate was administered. For the sugammadex (S) group, a higher intubating rocuronium dose (0.6 mg · kg^-1) was followed by 5-mg boluses each time the train-of-four count exceeded 2. Sugammadex (2-4 mg · kg^-1) was administered to reverse the block. All patients were extubated after obtaining a train-of-four ratio of 0.9.

MEASUREMENTS

The duration between the end of surgery and operating room discharge and the time spent in the postanesthesia care unit.

MAIN RESULTS

The time till operating room discharge was shorter and more predictable in group S (9.15±4.28 minutes vs 13.87±11.43 minutes in group N; P=.005). The maximal duration in group S was 22 minutes, compared with 72 minutes in group N. The time spent in the postanesthesia care unit was not significantly different (group S: 47.75±31.77 minutes and group N: 53.43±40.57 minutes; P=.543).

CONCLUSION

Maintaining a deep neuromuscular block during laparoscopic hysterectomy reversed at the end of the procedure with sugammadex enabled a faster and more predictable time till operating room discharge than did the classical combination of a shallower block reversed with neostigmine.

Electroencephalographic variation during end maintenance and emergence from surgical anesthesia

The re-establishment of conscious awareness after discontinuing general anesthesia has often been assumed to be the inverse of loss of consciousness. This is despite the obvious asymmetry in the initiation and termination of natural sleep. In order to characterize the restoration of consciousness after surgery, we recorded frontal electroencephalograph (EEG) from 100 patients in the operating room during maintenance and emergence from general anesthesia. We have defined, for the first time, 4 steady-state patterns of anesthetic maintenance based on the relative EEG power in the slow-wave (<14 Hz) frequency bands that dominate sleep and anesthesia. Unlike single-drug experiments performed in healthy volunteers, we found that surgical patients exhibited greater electroencephalographic heterogeneity while re-establishing conscious awareness after drug discontinuation. Moreover, these emergence patterns could be broadly grouped according to the duration and rapidity of transitions amongst these slow-wave dominated brain states that precede awakening. Most patients progressed gradually from a pattern characterized by strong peaks of delta (0.5-4 Hz) and alpha/spindle (8-14 Hz) power ('Slow-Wave Anesthesia') to a state marked by low delta-spindle power ('Non Slow-Wave Anesthesia') before awakening. However, 31% of patients transitioned abruptly from Slow-Wave Anesthesia to waking; they were also more likely to express pain in the post-operative period. Our results, based on sleep-staging classification, provide the first systematized nomenclature for tracking brain states under general anesthesia from maintenance to emergence, and suggest that these transitions may correlate with post-operative outcomes such as pain.

Limitations of anaesthesia depth monitoring

PURPOSE OF REVIEW

We critically review brain function monitors based on the processed electroencephalogram with regards to signal quality, artefacts and other limitations in clinical performance.

RECENT FINDINGS

Several studies have been showing that depth of anaesthesia monitors based on processed electroencephalogram has limitations that can lead to a wrong interpretation of the level of anaesthesia. Processed electroencephalogram indices can be altered by nonanaesthetic influences ranging from artefacts that affect signal quality and signal processing, adverse effects of some anaesthetic and nonanaesthetic drugs, neuromuscular blocking agents to conditions inherent to the patient such as cerebral tumours, brain ischemia and temperature.

SUMMARY

Clinicians should be aware of the several limitations of the commercial devices intending to monitor the depth of anaesthesia, which may not reflect the real underlying level of unconsciousness.

Elevated BIS and Entropy values after sugammadex or neostigmine: an electroencephalographic or electromyographic phenomenon?

BACKGROUND

Sugammadex is designed to antagonize neuromuscular blockade (NMB) induced by rocuronium or vecuronium. In clinical practice, we have noticed a rise in the numerical values of bispectral index (BIS) and Entropy, two electroencephalogram (EEG) - based depth of anesthesia monitors, during the reversal of the NMB with sugammadex. The aim of this prospective, randomized, double-blind study was to test this impression and to compare the effects of sugammadex and neostigmine on the BIS and Entropy values during the reversal of the NMB.

METHODS

Thirty patients undergoing gynecological operations were studied. Patients were anesthetized with target-controlled infusions of propofol and remifentanil, and rocuronium was used to induce NMB. After operation, during light propofol-remifentanil anesthesia, NMB was antagonized with sugammadex or neostigmine. During the following 5 min, the numerical values of BIS, BIS electromyographic (BIS EMG) and Entropy were recorded on a laptop computer, as well as the biosignal recorded by the Entropy strip. The Entropy biosignal was studied off-line both in time and frequency domain to see if NMB reversal causes changes in EEG.

RESULTS

In some patients, administration of sugammadex or neostigmine caused a significant rise in the numerical values of BIS, BIS EMG and Entropy. This phenomenon was most likely caused by increased electromyographic (EMG) activity. The administration of sugammadex or neostigmine appeared to have only minimal effect on EEG.

CONCLUSION

The EMG contamination of EEG causes BIS and Entropy values to rise during reversal of rocuronium-induced NMB in light propofol-remifentanil anesthesia.

Comparison of spectral entropy and BIS VISTA™ monitor during general anesthesia for cardiac surgery

OBJECTIVES

We compared the primary metrics of the Spectral entropy M-ENTROPY™ module and BIS VISTA™ monitor-i.e., bispectral index (BIS), state entropy (SE), and response entropy (RE) in terms of agreement and correlation during general anesthesia for cardiac surgery. We also evaluated responsiveness of electroencephalogram (EEG)-based and hemodynamic parameters to surgical noxious stimulation, skin incision, and sternotomy, hypothesizing that RE would be a better responsiveness predictor.

METHODS

BIS and entropy sensors were applied before anesthesia induction in 32 patients having elective cardiac surgery. Total intravenous anesthesia was standardized and guided by the BIS index with neuromuscular blockade tested with train-of-four monitoring. Parameters included SE, RE, BIS, forehead electromyography (EMG), and hemodynamic variables. Time points for analyzing BIS, entropy, and hemodynamic values were 1 min before and after: anesthesia induction, intubation, skin incision, sternotomy, cannulation of the aorta, cardiopulmonary bypass (CPB), cross-clamping the aorta, de-clamping the aorta, and end of CPB; also after starting the re-warming phase and at 10, 20, 30, and 40 min following.

RESULTS

The mean difference between BIS and SE (Bland-Altman) was 2.14 (+16/- 11; 95% CI 1.59-2.67), and between BIS and RE it was 0.02 (+14/- 14; 95% CI 0.01-0.06). BIS and SE (r(2) = 0.66; P = 0.001) and BIS and RE (r(2) = 0.7; P = 0.001) were closely correlated (Pearson's). EEG parameters, EMG values, and systolic blood pressure significantly increased after skin incision, and sternotomy. The effect of surgical stimulation (Cohen's d) was highest for RE after skin incision (-0.71; P = 0.0001) and sternotomy (-0.94; P = 0.0001).

CONCLUSION

Agreement was poor between the BIS index measured by BIS VISTA™ and SE values at critical anesthesia time points in patients undergoing cardiac surgery. RE was a good predictor of arousal after surgical stimulation regardless of the surgical level of muscle relaxation. Index differences most likely resulted from different algorithms for calculating consciousness level.